Capacitor constructions are common circuit devices. Capacitor constructions are utilized in, for example, dynamic random access memory (DRAM) cells of integrated circuits. The DRAM cells typically comprise a charge storage capacitor coupled to an access device, with the typical access device being a metal-oxide-semiconductor field effect transistor (MOSFET).
A continuing goal in integrated circuit device fabrication is to increase performance of circuit devices without increasing the amount of real estate consumed by the devices. For capacitor devices, such goal can manifest as a desire to increase the total charge capacity of a capacitor device without significantly affecting the cell area consumed by the device. New capacitor dielectric materials with high dielectric constants (so-called high-k materials) have been introduced to replace conventional dielectric materials, such as, for example, silicon nitride and silicon dioxide. Thin films of the high-k materials can be utilized in capacitor devices to obtain high capacitance while maintaining, or even reducing, the footprint of the devices relative to previous devices that utilized lower k dielectric materials.
High-k dielectric materials are typically understood to be materials having a dielectric constant greater than that of silicon dioxide, with exemplary high-k materials being Al2O3 (aluminum oxide), Ta2O5 (tantalum pentoxide), barium titanate (BT), strontium titanate (ST), lead zirconate titanate (PZT), bismuth strontium titanate (BST), HfOx (hafnium oxide) and ZrOy (zirconium oxide). The x in HfOx and the y in ZrOy are numbers greater than zero, and typically less than or equal to 2.
Although the high-k dielectric materials described above can provide numerous advantages when utilized in capacitor constructions, there are difficulties associated with the materials which can offset the benefits gained by utilizing the materials. One problem encountered when incorporating high-k materials into current DRAM cell designs is that chemical reactivity between the high-k materials and other materials of a DRAM cell can impede performance of the cell, and even destroy operability of the cell. For instance, numerous of the high-k materials are formed under strongly oxidizing conditions, and such conditions can oxidize electrode components which are intended to be incorporated into capacitor constructions with the high-k materials. The oxidized electrode components can have reduced electrical conductivity relative to non-oxidized components, which can impair operability of the resulting capacitor cell, and in some cases can lower the total capacitance of resulting capacitor below acceptable tolerances.
It would be desirable to develop new methods for incorporating high-k dielectric materials into capacitor constructions.